Pd/Fe nanoparticle integrated PMAA-PVDF membranes for chloro-organic remediation from synthetic and site groundwater.

The poly(methacrylic acid) (PMAA) was synthesized in the pores of commercial microfiltration PVDF membranes to allow incorporation of catalytic palladium/iron (Pd/Fe) nanoparticles for groundwater remediation. Particles of 17.1 ± 4.9 nm size were observed throughout the pores of membranes using a focused ion beam. To understand the role of Pd fractions and particle compositions, 2-chlorobiphenyl was used as a model compound in solution phase studies. Results show H2 production (Fe0 corrosion in water) is a function of Pd coverage on the Fe. Insufficient H2 production caused by higher coverage (> 10.4% for 5.5 wt%) hindered dechlorination rate. With 0.5 wt% Pd, palladized-Fe reaction rate (surface area normalized reaction rate, ksa = 0.12 L/(m2-h) was considerably higher than isolated Pd and Fe particles. For groundwater, in a single pass of Pd/Fe-PMAA-PVDF membranes (0.5 wt% Pd), chlorinated organics, such as trichloroethylene (177 ppb) and carbon tetrachloride (35 ppb), were degraded to 16 and 0.3 ppb, respectively, at 2.2 seconds of residence time. The degradation rate (observed ksa) followed the order of carbon tetrachloride > trichloroethylene > tetrachloroethylene > chloroform. A 36 h continuous flow study with organic mixture and the regeneration process show the potential for on-site remediation.

Reductive Degradation of CCl4 by Sulfidized Fe and Pd-Fe Nanoparticles: Kinetics, Longevity, and Morphology Aspects.

In this study a systematic comparison in morphology, long-term degradation, regeneration and reuse were conducted between palladized and sulfidized nanoscale zero-valent iron (Pd-Fe and S-Fe). Pd-Fe and S-Fe were prepared, after the synthesis of precursor Fe0 nanoparticles (spherical, ~35 nm radius) for carbon tetrachloride (CTC) treatment. With HAADF-TEM-EDS characterization, dispersive Pd islets were found on the Fe core of Pd-Fe. However, the Fe core was covered by the FeSx shell of S-Fe (FeS/FeS2 = 0.47). With an excessive Pd dose (10 mol%), the Pd-Fe were dramatically deformed to dendritic structures which significantly decreased reactivity. For CTC degradation, Pd-Fe (0.3 atomic% Pd) increased the degradation rate by 20-fold (ksa= 0.580 Lm-2min-1) while S-Fe presented a greater life time. The major intermediate chloroform (CF) was further degraded and less than 5% CF was observed after 24 h using Pd-Fe or S-Fe while above 50% CF remained using Fe. During aging, the Fe core was converted to FeOOH and Fe3O4/γ-Fe2O3. The restoration of Fe0 was achieved using NaBH4, which regenerated Fe and Pd-Fe. However, the formed FeSx shell on S-Fe was disappeared. The results suggest that S-Fe extends longevity of Fe, but the loss of FeSx after aging makes S-Fe eventually perform like Fe in terms of CTC degradation.

Luffa cylindrica (Sponge Gourd) Fibers in Treatment of Greywater: an Aerobic Fixed-Film Reactor Approach.

The need for potable water consumption in urban and suburban regions can be decreased by greywater treatment and its reuse. Utilizing natural fibers may provide sustainable solutions in addressing challenges related to water resource management. In this study, a fixed-film reactor was designed with Luffa cylindrica (an annually occurring fruit) as a bio-carrier. The lab-scale reactors were configured with and without Luffa cylindrica and were run for 90 days in fed-batch mode. Scanning electron microscopy (SEM) was performed to validate biofilm production over time. Monitoring COD, nitrogen, and total phosphate removal allowed for analysis of treatment effectiveness. Results demonstrated the treatment efficiency for the experimental reactor was 70.96%, 97.02%, 92.57%, and 81.20% for COD, nitrogen, phosphate, and anionic surfactant (AS), respectively. 16 s rRNA gene sequencing of bio-carrier and control greywater samples was carried out. Many bacteria known to break down anionic surfactants were observed, and microbial succession was witnessed in the control reactor vs. the experimental reactor samples. The three most prevalent genera in the experimental samples were Chlorobium, Chlorobaculum, and Terrimonas. However, it is crucial to underscore that additional research is essential to solidify our understanding in this domain, with this study laying the fundamental groundwork.

Effects of incineration and pyrolysis on removal of organics and liberation of cathode active materials derived from spent ternary lithium-ion batteries.

Removing organics via thermal treatment to liberate active materials from spent cathode sheets is essential for recovering lithium-ion batteries. In this study, the effects of incineration, N2 pyrolysis, and CO2 pyrolysis on the removal of organics and liberation of ternary cathode active materials (CAMs) were compared. The results indicated that the organics in the spent ternary cathode sheets comprised a residual electrolyte and polyvinylidene fluoride (PVDF) binder. Moreover, the organics could be removed to promote the liberation of CAMs via incineration, N2 pyrolysis, and CO2 pyrolysis. When the temperature was <200 °C, the chemical properties of the volatilized ester electrolyte remained unchanged during both N2 and CO2 pyrolysis, indicating that the electrolyte can be collected by controlling the pyrolysis temperature and condensation. Furthermore, PVDF binder decomposition occurred at 200-600 °C. The optimal temperatures of incineration, N2 pyrolysis, and CO2 pyrolysis were 550, 500, and 450 °C, respectively, and these treatments increased the liberation efficiency of CAMs from 81.49 % to 98.75 %, 99.26 %, and 97.98 %, respectively. In addition, heat-treated CAMs required less time to achieve adequate liberation. Following three thermal treatment processes, the sizes of the CAM particles were mainly concentrated in the ranges of 0.075-0.1 mm and <0.075 mm. Furthermore, for all types of CAMs examined, the Al concentration decreased from 1.09 % to <0.35 %, which increased the separation efficiency and improved the chemical metallurgical performance.

A double-edged sword: Constructed wetland-microbial fuel cells promote organics removal via entrapment.

Recently, constructed wetland-microbial fuel cells (CW-MFCs) are found to enhance the organics removal via the connection of the external circuit. Yet, it is unclear why the energy output is unmatched with the enhancement of the organics removal. This study compared the dynamic changes of the organics in a CW-MFC microcosm operated under the close circuit and open circuit. As a result, the close circuit facilitated the organics removal by 9 % before the proportional discharge of carbon metabolites. This suggested that organics entrapment should account for the huge loss of carbon recovery; and closing the external circuit could further promote the organics entrapment. Besides, polyhydroxybutyrate was found accumulated in the MFC culture experiment, evidencing that the fed-batch mode of operation could result in a feast-famine pattern of microbial metabolism. Despite the fast organics entrapment during the first hours, prolonging the operation time would lead to continuous carbon gas emission, along with the substantially elevated coulombic efficiency. Together, these results explained the substantial COD removal enhancement with low electricity yield, and cautioned the safe use of the MFC integration to spare the system from overaccumulation of organics.

The coupling system of magnetite-enhanced thermophilic hydrolysis-acidification and denitrification for refractory organics removal from anaerobic digestate food waste effluent (ADFE).

The aim of this study was to remove the refractory organics from high-temperature anaerobic digestate food waste effluent by the coupling system of hydrolysis-acidification and denitrification. Iron-based materials (magnetite, zero-valent iron, and iron-carbon) were used to enhance the performance of thermophilic hydrolysis-acidification. Compared with the control group, magnetite had the best strengthening effect, increasing volatile fatty acids concentration and fluorescence intensity of easily biodegradable organics in the effluent by 47.6 % and 108.4 %, respectively. The coupling system of magnetite-enhanced thermophilic hydrolysis-acidification and denitrification achieved a nitrate removal efficiency of 91.2 % (influent NO3--N was 150 mg L-1), and reduced the fluorescence intensity of refractory organics by 33.8 %, compared with influent. Microbiological analysis indicated that magnetite increased the relative abundance of thermophilic hydrolytic acidifying bacteria, and coupling system enriched some genera simultaneously removing nitrate and refractory organics. This study provided fresh information on refractory organics and nitrogen removal of thermophilic wastewater biologically.

Recent insights into greywater treatment: a comprehensive review on characteristics, treatment technologies, and pollutant removal mechanisms.

With the rapid socio-economic and industrial development, the problem of water shortage is becoming increasingly serious. Seeking alternative water sources to reduce the need for freshwater resources is an increasing concern. Household greywater production is high and accounts for about 50-80% of domestic wastewater. In recent years, the in situ treatment and reuse of greywater have received widespread attention. Treated greywater can be used for non-potable purposes such as toilet flushing and irrigation, which can greatly reduce the pressure of freshwater resource shortage. This paper reviews the sources and characteristics of greywater and analyzes its quantity and quality. In addition, this paper outlines and summarizes various greywater treatment technologies commonly used, including physical, biological, and chemical treatment technologies, as well as combination technologies. Understanding the mechanisms of contaminant removal is essential for effective greywater treatment. While discussing different treatment technologies, we focus on the removal mechanisms of pollutants from greywater, including organics, nutrients, surfactants, and emerging contaminants. Finally, future perspectives on greywater management and reuse are presented. Through a comprehensive review, we expect that this review will help the reader to better understand the characteristics of greywater and to more rationally select the appropriate treatment technology based on the removal mechanism of pollutants.

MEUF for removal and recovery of valuable organic components present in effluents: A process intensified technology.

In recent years, the domain of the research space in novel separation process has been led by membrane systems as a panacea providing multifarious benefits of high separation efficiency, elimination of extreme process conditions, sustainability, and environment friendliness coupled with high operational flexibility. In this niche area, often, ultrafiltration is touted as a robust separation technique due to its high separation efficiency, membrane stability, and lower operating costs. The only drawback of relatively large pore size can be overcome by combining surfactant addition, leading to development of integrated processes termed as Micellar Enhanced Ultrafiltration. MEUF processes isolate and selectively separate valuable organics present in effluent streams. The process characteristics fit the bill as a typified example for process intensification Technology interventions for recycling of surfactants can enhance the cost-competitiveness of the process. This has the potential to develop into a broad-spectrum effluent treatment option with a change of surfactants for target contaminants. Here, in this review, we attempt to critically examine the unique features of this technology, development of spin-offs with wide-ranging applications. Specifically applications in removal of hazardous, and persistent components like dissolved organics have been critically studied. The focus was to highlight the crux of the novel technologies highlighting the efficacy and the underlying concept of process intensification. PRACTITIONER POINTS: Role of MEUF as a sustainable process intensifying separation technique for removal and recovery of organics. Novel process development using MEUF. Comparative performance analysis to assess efficacy. Discussions on future integrative process development. Sustainability aspect of MEUF with possibility of byproduct recovery.

Advances in elemental sulfur-driven bioprocesses for wastewater treatment: From metabolic study to application.

Elemental sulfur (S0) is known to be an abundant, non-toxic material with a wide range of redox states (-2 to +6) and may serve as an excellent electron carrier in wastewater treatment. In turn, S0-driven bioprocesses, which employ S0 as electron donor or acceptor, have recently established themselves as cost-effective therefore attractive solutions for wastewater treatment. Numerous related processes have, to date, been developed from laboratory experiments into full-scale applications, including S0-driven autotrophic denitrification for nitrate removal and S0-reducing organic removal. Compared to the conventional activated sludge process, these bioprocesses require only a small amount of organic matter and produce very little sludge. There have been great efforts to characterize chemical and biogenic S0 and related functional microorganisms in order to identify the biochemical pathways, upgrade the bioprocesses, and assess the impact of the operating factors on process performance, ultimately aiming to better understand and to optimize the processes. This paper is therefore a comprehensive overview of emerging S0-driven biotechnologies, including the development of S0-driven autotrophic denitrification and S0-based sulfidogenesis, as well as the associated microbiology and biochemistry. Also reviewed here are the physicochemical characteristics of S0 and the effects that environmental factors such as pH, influent sulfur/nitrate ratio, temperature, S0 particle size and reactor configurations have on the process. Research gaps, challenges of process applications and potential areas for future research are further proposed and discussed.

Microalgal-bacterial granular sludge process outperformed aerobic granular sludge process in municipal wastewater treatment with less carbon dioxide emissions.

The aerobic granular sludge (AGS) process and microalgal-bacterial granular sludge (MBGS) process were comparably applied for municipal wastewater treatment in sequencing batch reactors with a height to diameter ratio of eight. For morphological appearances, the yellow aerobic granules were strip-shaped (4.0 mm × 0.62 mm) while the green microalgal-bacterial granules were elliptical-shaped (2.0 mm × 0.75 mm). The dominated rod-shaped bacteria (e.g., Acidobacteria and Bacteroidetes) and the slender configuration might be associated with the strip shape of aerobic granules under weak acid conditions. The nutrients removal performances by MBGS process were generally slightly better than AGS process. In addition, nutrients removal mechanisms were identified to elucidate how organics, ammonia, and phosphorus were removed by AGS process and MBGS process, respectively. Mass balance calculation estimated that MBGS process appeared to achieve much less CO2 emission (5.8%) compared with AGS process (44.4%). Overall, it proved that MBGS process, with the merits of potentially low energy cost, limited CO2 emission, and excellent performance, showed more prospects in municipal wastewater treatment than AGS process.

Improving the performance of vertical flow constructed wetlands by modifying the filtering media structure.

The aim of this research was to study the influence of the bed media configuration and particle size on the treatment efficiency of subsurface vertical flow (VF) constructed wetlands (CWs) treating municipal wastewater. Two outdoor pilot units (VF1 and VF2, planted with Phragmites australis) with the configuration C1 were operated in parallel for 2 years at similar surface loading rates of 9.7 ± 3.2 (VF1) and 10.1 ± 3.3 (VF2) g biological oxygen demand (BOD5)/m2·day (19.5 ± 6.4 (VF1) and 20.4 ± 6.2 (VF2) g chemical oxygen demand (COD)/m2·day). A different configuration C2 was used during the third year at 16.9 ± 4.6 (VF1) and 18.2 ± 3.0 (VF2) g BOD5/m2·day and 26.0 ± 7.2 (VF1) and 28.0 ± 4.7 (VF2) g COD/m2·day. Two different filtering materials (1-3-mm sand for VF1 and 2-6-mm fine gravel for VF2) were used for configuration C1. The same units were modified after 2 years of operation by adding a 10-cm layer of fine sand (0-2 mm) on the top (configuration C2). In C1 conditions, the unit with the coarse material VF2 showed significantly (p < 0.05) lower removal efficiencies of total suspended solids (TSS) and BOD5 than VF1, and both units failed to meet the BOD5 discharge limit. In C2 conditions, removal efficiencies reached 82% TSS, 97% BOD5, 76-81% ammonia, and 60-66% TN, without significant differences between VF1 and VF2 units. Removal efficiencies were significantly higher for configuration C2 than that for C1, due to the positive effect of the upper fine sand layer. The presence of this fine sand layer doubled the water retention time and increased the removal rates, while the infiltration rates were high enough for an operation free of clogging.

Reverse osmosis concentrate treatment by microbubble ozonation-biological activated carbon process: Organics removal performance and environmental impact assessment.

Reverse osmosis (RO) is being used in many water reclamation facilities to produce high quality water that can be reused for different purposes. As a part of the RO process, a reject stream is produced as the reverse osmosis concentrate (ROC), which contains elevated levels of contaminants compared to the source water. Effective treatment and safe disposal of ROC via cost-effective means is very challenging. This study aims to develop a robust microbubble ozonation-biological process for industrial ROC treatment with a target effluent chemical oxygen demand (COD) lower than 60 mg/L. As compared to macrobubble ozonation, microbubble ozonation exhibited better ozone dissolution and 29% higher COD removal efficiency with the same ozone dosage. Under the optimum operating conditions with ozone dosage of 30 mg/L, ROC natural pH of 8.67 and ozonation duration of 1 h, microbubble ozonation achieved 42% COD removal efficiency while increasing the BOD5/COD ratio (ratio of biological oxygen demand over 5 days to the corresponding chemical oxygen demand) in ROC from 0.042 to 0.216. A biological activated carbon (BAC) column with an empty bed contact time (EBCT) of 120 min was combined with microbubble ozonation for continuous ROC treatment. Over the 100-day operation, the combined system performed consistent organics removal with an average effluent COD of 45 mg/L. Both LC-OCD data and fluorescence EEM spectra confirmed humic substances were the dominant organic species in ROC. Ozone pre-treatment could achieve significant removal of humic substances in raw ROC. ATP analysis found that ozone pre-treatment enhanced BAC biofilm activity by around 5 folds. 5 min acute toxicity assessment with Aliivibrio fischeri showed 4 times reduction of bioluminescence inhibition in ozone treated ROC. From the environmental point of view, Life cycle assessment (LCA) results demonstrated that Ozone-BAC system had significant environmental burdens on climate change and human toxicity due to the electricity production process. These environmental impacts can be mitigated by optimizing the ozonation process with reduced ozone dosage or utilizing renewable energy sources for electricity generation.

Simulation of FBR-Fenton/GAC process for recalcitrant industrial wastewater treatment with a computational fluid dynamics-kinetic model framework.

An integrated computational fluid dynamics (CFD)-kinetic model framework was developed to numerically describe the hydrodynamic and kinetic phenomena in a liquid-solid two phases Fluidized-bed reactor Fenton/granular activated carbon (FBR-Fenton/GAC) system. The model obtained excellent accuracy for predicting chemical oxygen demand (COD) removal in reverse osmosis concentrate (ROC) treatment under different operation conditions. Hydrodynamic evaluation demonstrated that under the quasi-steady state, the GAC particles were uniformly circulated in the bed region with two pairs of counter-rotating recirculation cells, and a clear interface layer formed between the solid and the liquid phases. Superficial liquid velocity highly affected the fluidized bed expansion and solid volume fraction, while its impact on the overall COD removal efficiency was negligible. Chemical evaluation revealed that GAC/H2O2 catalytic reaction enhanced the •OH production in FBR-Fenton/GAC process by 2.7 folds as compared to homogenous Fenton process. Fenton reaction mainly occurred in the upper liquid region and its kinetics for •OH generation significantly diminished by 75% within the first 10 min. GAC/H2O2 reaction took place in the fluidized bed region for continuous •OH generation with a relatively stable rate from 1.21 × 10-6 to 0.60 × 10-6 M/s. Along the ROC treatment with FBR-Fenton/GAC process, the simulated COD degradation rate decreased along the reaction time with 2.05 × 10-6 M/s and 2.93 × 10-7 M/s at 2 min and 60 min, respectively. Faster COD removal was attained in the fluidized bed region due to combining effects of •OH oxidation and GAC adsorption. The overall predicted COD concentration reduced from 122 to 35 mg/L, •OH oxidation and GAC adsorption contributed 59% and 41%, respectively, to the total COD removal.

Fluidized-bed Fenton technologies for recalcitrant industrial wastewater treatment-Recent advances, challenges and perspective.

In recent years, fluidized-bed Fenton (FBR-Fenton) process has gained more attention in treating recalcitrant industrial wastewater. FBR-Fenton combines the effectiveness of homogeneous Fenton and sludge reduction of heterogeneous Fenton. Comparing to other modified Fenton processes, FBR-Fenton has greater economical and scaling up potential. However, large consumption of Fenton reagents and strict pH control are still the bottlenecks hampering the full-scale application of FBR-Fenton. While prior reviews mainly focused on the operation and performance of FBR-Fenton process, the present study critically discussed the challenges and bottlenecks for its full-scale industrial application. This study also comprehensively reviewed the development strategies for tackling these drawbacks, mainly over the recent five years. Homogeneous FBR-Fenton, heterogeneous FBR-Fenton and heterogeneous FBR-photo-Fenton processes were classified for the first time according to their reaction mechanisms and system designs. Important operational and design parameters affecting the cost-effectiveness of all FBR-Fenton technologies were reviewed, including the fundamentals, common practices and even innovative steps for enhancing the process performance. Up-to-date applications of FBR-Fenton technologies in recalcitrant wastewater/compounds treatment were also summarized, and it was found that upscaling of heterogeneous FBR-Fenton and heterogeneous FBR-photo-Fenton processes was still very challenging. Strategies to overcome the key technical limitations and enhance process cost-effectiveness were discussed in the future perspective part. Furthermore, modelling techniques such as computational fluid dynamics model and artificial neural network were suggested to be promising modelling techniques for speeding up the full-scale applications of FBR-Fenton technologies.

Residual organics removal from manganese electrochemical solution using combined Fenton oxidation process with adsorption over activated carbon.

The removal of residual organics from manganese (Mn) electrochemical solution using combined Fenton oxidation process with adsorption over activated carbon (AC) was investigated. The effect of operating conditions such as dosage of H2O2, H2O2/Fe2+ ratio, initial pH value, reaction temperature, and reaction time on Fenton oxidation was studied. Experimental results indicated that a maximum chemical oxygen demand (COD) of 83.2% was obtained under the optimized set of conditions: H2O2 concentration of 0.15 mol/L, H2O2/Fe2+ molar ratio of 3, initial pH value of 3, reaction temperature of 50 °C, and reaction time of 90 min. The leaching solution was furthered treated over AC and COD removal rate increased to 93.1% under 3.75 g/L dosage of AC, adsorption temperature of 70 °C, and adsorption time of 120 min. The adsorption mechanism of Mn over AC was detailly investigated, while the porous texture of AC was studied by nitrogen adsorption isotherm.

Advanced oxygenation efficiency and purification of wastewater using a constant partially unsaturated scheme in column experiments simulating vertical subsurface flow constructed wetlands.

The presence of sufficient dissolved oxygen (DO) in a constructed wetland (CW) is vital to the process of removing ammonia nitrogen and organics from wastewater. To achieve total nitrogen removal, which is characterised by enhanced ammonia nitrogen removal, this study offers an efficient strategy to increase the oxygen supply by establishing constant unsaturated zones and baffles in simulating constructed wetlands (SCWs). Henceforth, this strategy is addressed as a partially unsaturated SCW. A centrally located high tube was set up inside the wetland to create an unsaturated zone at a higher level. The effectiveness of the unsaturated zone to supplement the oxygen content was evaluated by comparing with controls (an unaerated SCW and an aerated SCW). The results show the chemical oxygen demand removal rate (85 ±â€¯6%) in the partially unsaturated SCW was equivalent to that in the aerated SCW (83 ±â€¯6%), while the ammonia nitrogen removal rate was 11 times higher compared to that of the unaerated SCW. The removal potential of the partially unsaturated SCW under different HRT (hydraulic retention time)s (12, 24, and 36 h) was examined, and the 36 h-SCW performed the best in the removal of organics and nitrogen. The mechanisms behind the unsaturated zone strategy were studied by analysing water and microbe samples along the pathway. The results from the water quality indicators and the quantitative polymerase chain reactions along the pathway showed the unsaturated zone contributed to the removal of primary organics and ammonia nitrogen. The superior performance of unsaturated zone strategy was discussed further using the enrichment of ammonia-oxidising bacteria, mass of oxygen uptake, and baffle design. The results indicate that the amoA gene/16s rRNA gene abundance ratio and the oxygen uptake (336 ±â€¯44 g m-3 d-1) in the partially unsaturated SCW was higher than that observed in the two controls.

Coupling of thermophilic biofilm-based systems and ozonation for enhanced organics removal from high-temperature pulping wastewater: Performance, microbial communities, and pollutant transformations.

This study focused on the establishment of thermophilic biofilm-based systems (TBSs) coupled with ozonation for treatment of high-temperature pulping wastewater. The effects of the inoculum, sludge growth mode, and temperature were investigated. These factors played roles in the organics removal performance and microbial communities of pulping wastewater treatment systems. At 50 °C, the TBS inoculated with optimal inoculum achieved 59.12% and 37.96% reductions in COD and chromaticity, which were superior to the reductions achieved by other systems. In this TBS, thermophilic lignocellulolytic microorganisms (Chloroflexus, Meiothermus, norank_f_Caldilineaceae, and Roseiflexus) and carbohydrate-fermenting bacteria (norank_f_Anaerolineaceae) were predominant. Their relative abundances were 25.55% and 10.42%, respectively. For enhanced removal of COD and chromaticity, an integrated system consisting of a primary TBS, ozonation, and a secondary TBS was proposed. The total COD and chromaticity removal efficiencies increased to 90.48% and 87.89%, respectively. BOD5/COD increased from 0.20 to 0.40, and shifts of lignin-like and humic acid-like substances were observed during ozonation with the primary TBS effluent.

Organics removal and in-situ granule activated carbon regeneration in FBR-Fenton/GAC process for reverse osmosis concentrate treatment.

Fluidized bed reactor Fenton (FBR-Fenton) process was adopted for reverse osmosis concentrate (ROC) treatment with three types of carriers, including sand, zeolite and granular activated carbon (GAC). Adsorption studies demonstrated that GAC achieved the best adsorption performance (maximum COD removal of 78% in 15 h) among the three carriers, and the adsorption of ROC organic matters followed a two-stage adsorption model. Fenton oxidations were carried out in three fluidized beds after column saturation, and FBR-Fenton/GAC process achieved highest COD removal (72%) and most BOD5/COD ratio enhancement (from 0.03 to 0.3) in ROC. Long-term operation data demonstrated good performance stability of GAC as the carrier. In addition, GAC fluidized bed obtained highest total iron removal rate via iron crystallization process. Continuous in-situ GAC regeneration with more than 90% recoveries of surface area, pore volume and adsorption capacity were observed along the ROC treatment with FBR-Fenton/GAC process. Mechanism studies revealed that better COD removal performance in FBR-Fenton/GAC process was attributed to the combining effects of homogenous Fenton reaction, GAC adsorption and GAC/H2O2 catalytic reaction.

Simultaneous partial nitrification, anammox and denitrification (SNAD) process for nitrogen and refractory organic compounds removal from mature landfill leachate: Performance and metagenome-based microbial ecology.

In this study, a simultaneous partial nitrification, Anammox and denitrification (SNAD) bioreactor was constructed for mature landfill leachate treatment, which exhibited favorable NH4+-N (98.9-99.9%), TN (90.7-94.9%) and bio-refractory organic compounds (46.2-67.7%) removal efficiencies. Stoichiometric analysis demonstrated that the synergy of ammonium-oxidizing bacteria and Anammox bacteria dominated TN removal (96.1-97.2%). NO3--N produced in Anammox could be further reduced through (partial) denitrification and dissimilatory nitrate reduction to ammonium (DNRA). The results highlighted that humic-like and their intermediates might serve as the electron donor for these (partial) denitrifiers and DNRA bacteria to remove NO3--N, and could be effectively removed from mature landfill leachate in SNAD bioreactor. Metagenomic characterization further demonstrated that phyla Chloroflexi, Chlorobi and genera Nitrosomonas, Ignavibacterium and Aminiphilus might be responsible for such humic-like degradation. Overall, this work offers new insights into the metagenome-based bioinformatic roles for the previously understudied microorganisms in SNAD bioreactor for mature landfill leachate treatment.

Biofilter scaling procedures for organics removal: A potential alternative to piloting.

To provide information for the design and improvement of full-scale biofilters, pilot-scale biofiltration studies are the current industry standard because they utilize the same filter media size and loading rate as the full-scale biofilters. In the current study, bench-scale biofilters were designed according to a biofilter scaling model from the literature, and the ability of the bench-scale biofilters to accurately represent the organics removal of pilot-scale biofilters was tested. To ensure similarity in effluent water quality between bench- and pilot- or full-scale biofilters at the same influent substrate concentration, the tested model requires that either mass transport resistance or biofilm shear loss takes primacy over the other. The potential primacy of mass transport resistance or biofilm shear loss was evaluated via water quality testing (dissolved organic carbon, specific ultraviolet absorbance, liquid chromatography - organic carbon detection, trihalomethane formation potential, and haloacetic acid formation potential). The biofilters also were characterized for adenosine triphosphate (ATP) content, enzyme activity, extracellular polymeric substances, and microbial community structure. The results of this study indicate that biofilm shear loss takes primacy over mass transport resistance for bench-scale biofilter design in this system; thus, bench-scale biofilters designed in this manner accurately represent organics removal in pilot-scale biofilters. Applying this scaling procedure can reduce filter media requirements from many kilograms to just a few grams and daily water requirements from thousands of liters to less than 10 L. This scaling procedure will allow future researchers to test alternative treatment designs and operating conditions without the need for expensive pilot-scale studies.